Inkjet printers which perform a printer operation by ejecting ink droplets onto a recording medium are known in the art. The known inkjet printers include an inkjet head which includes a reservoir for storing ink, a common ink chamber which receives ink from the reservoir, and a plurality of separate ink passages which extend from the common ink chamber to nozzles via a pressure chamber. In the known inkjet head, ink is supplied to the reservoir via an ink channel which is connected to an ink supply port. When the inkjet head is filled with ink, residual air may remain with ink in the ink channel and inside the pump for feeding the ink. The residual air may flow into the reservoir via the ink supply port, which may cause the nozzles to become clogged. If the nozzles become clogged, the performance of the nozzles deteriorates with respect to ejecting ink.
To address this problem, another known inkjet head is provided with a discharge passage that discharges the air that flows into the reservoir along with the ink to the outside. This known inkjet head has a supply port for supplying ink, which is positioned adjacent to one end in the longitudinal direction, and a discharge port for discharging ink, which is positioned adjacent to the other end. In addition, a reservoir is positioned within the inkjet head, which extends in the longitudinal direction from the supply port, and the discharge passage extends from a downstream side of the reservoir to the discharge port. As a result, when the discharge port is open and ink is supplied from the supply port, air that remains in the reservoir may be discharged along with the ink to the outside via the discharge passage and the discharge port.
In this known inkjet head, with respect to the longitudinal direction, the supply port and the discharge port are positioned in the vicinity of opposite ends of the inkjet head. Consequently, connecting ink channels to the supply port and the discharge port may be complicated, and the arrangement of the ink channels connected to the supply port and the discharge port also may be complicated. Moreover, an ink passage including the reservoir and the discharge passage substantially extends throughout the entire length of the inkjet head in the longitudinal direction. As a result, there are design constraints with respect to the ink passage.